To clean bulb sockets I take a green scrubbie (scotchbrite pad) and cut a strip off the end about 3/4"-1" wide. Roll it up like a doobie and tightly wrap electrical tape around it leaving the last half inch or so sticking out on each end.

alot of the time it's not the dirt, it's that the socket has a bad ground through the bracket to the ground wire on the back of the playfield.

http://www.pinrepair.com/em/index2.htm#connect -Scroll down past the jones plugs section.

gtblamp1.jpg

EDIT: Don and I must have posted at the same time. The picture above is exactly what he is describing. I wish there was a tool to just re-press the socket back onto the bracket, I think that would solve most of the issues with old sockets.

I try to repair them when I can, usually rust is my determining factor as to whether or not I repair or replace. You can clean that flux up with a q-tip and some naptha.